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This page evaluates the ECMWF CKD tool "ecCKD", which builds on the methods described by Hogan (JAS 2010) and is under active development; the latest longwave results are from version is 0.5 and the shortwave results from version 0.6. CKD models are generated from CKDMIP datasets using the following automated steps:

• The band structure is specified, and then within each band the high-resolution absorption spectrum of each individual gas is reordered using the median/present-day concentration case from the MMM dataset, with the ordering according to the height of the peak cooling rate in the longwave, and the height at which the optical depth from TOA reaches 0.25 in the shortwave. For the NWP applications, all gases except H₂O and O₃ are merged into a single "composite" gas. Note that the same ordering is used at all heights.
• An error tolerance is specified by the user, and the reordered spectra for each gas are divided into as many k terms (g points) as are needed so that the RMSE in heating rate for any individual k term is less than the specified tolerance. The partitioning of the spectrum is adjusted so that the error associated with each k term in a band (for  single gas) is approximately equal. 
• The k terms for the individual gases are combined to obtain a final set of k terms using the hypercube partition method of Hogan (2010).
• The Idealized dataset is used to compute a the look-up tables of absorption coefficient for each gas in each k term.
• A quasi-Newton scheme is used to optimize the coefficients of the look-up table to minimize the errors when computing heating rates and fluxes for the Evaluation-1 dataset.

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Shortwave CKD models have been constructed with a range of k terms using the wide and narrow CKDMIP band structures. The full-spectrum correlated-k method was tried but the results are not yet satisfactory. As in the longwave, the CKD models are optimized by minimizing the errors against the Evaluation-1 CKDMIP line-by-line dataset, so the evaluations here are not yet truy truly independent. The full set of plots are available in PDF files for each of the three CKDMIP "applications":

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